Removal of heavy metals from aqueous solution by polyacrylic acid enhanced ultrafiltration

One of the recently developed water treatment processes is the polyelectrolyte-enhanced ultrafiltration (PEUF). This technique combines a membrane filtration process (ultratfiltration) and a cation-polyectrolyte complexation technique. PEUF is shown to be an efficient technology for the removal of heavy metals from liquid effluents even at low concentrations. In this proposal, the removal of three heavy metals (cadmium, copper and zinc) from aqueous solutions by PEUF process was investigated. The poly(acrylic acid) (PAA) with an average molecular weight 100kDa was used as complexing agent. The ultrafiltration experiments were performed using a tangential cell system equipped with a polyethersulphone membrane having a 10.000 molecular weight cut-off (MWCO). To improve the retention of the heavy metal ions, the effect of some operating parameters and solution characteristics were studied. For different PAA concentrations, this study showed that all permeate fluxes increased linearly by increasing transmembrane pressure. For the three studied metals, the best retentions were observed at 2x10(-3)mol L-1 PAA concentration, 3bar transmembrane pressure and pH above 5. The removal of cadmium, copper and zinc exceeded, respectively, 80, 93 and 70%.